Improvement in variable tube-gear



Y b21/mfom @a a ya /9/4? AW Q@ Al. PHOTO-LITRO. C0. N.Y. (SBORNE'SPROCESS.)

UNITED STATES PATENT OFFICE.

GEORGE DODDS AND ELIHU DODDS, OF ALLEGHENY, PENNSYLVANIA.

IMPROVEMENT IN VARIABLE TUBE-GEAR..

.To all whom t may concern,.-

Be known that we, GEORGE DoDDs and ELIHU DODDs, of the city ofAllegheny, in the I county of Allegheny and State of Pennsylvania, haveinvented a new and useful Improvement in Variable Out-Offs forSteam-Engines; i and we do hereby declare the following to be a full,clear, and exact description thereof, reference being had to theaccompanying drawings, forming part of this specification, in which- IFigure l is a vertical section through the cut-off apparatus andsteam-chest. Fig. 2 is a top view of the cams and cam-yoke of thecut-off apparatus, being a horizontal section through x x, Fig. l. Fig.3 is a perspective representation of the upper or cnt-oft' cams. Fig. 4is a perspective representation of the spiral cylinder by which thevariation of the cut ott' cams is effected. Fig. 5 is a vertical sectionthrough the hollow crown-wheel shaft and spiral cylinder at right anglesto the section in Fig. 1.

In the several figures like letters of reference denote similar' parts.

Our invention consists in the use and adaptation of certain mechanicalcontrivances for 1 the purpose of operating the independent cutoft'valve in steam-engines in such a manner that the point of the stroke ofthe piston at which the steam is cut off shall be variable throughoutthe length of the stroke, and so that the point of cutoff shall changewith the increased or diminished force of steam, exactly in proportionto the rapidity of stroke of the engine, thus forming a variablecut-off, which may also be rendered adjustable.

To enable others skilled in the art to construct a-nd use our invention,we will proceed to describe the construction and operation of ourcut-off apparatus.

In Fig. l, a is the cylinder of the steamengine, and b the piston. c isthe steam-chest. d is the working slide-valve, above which is ,f placedthe cutoff valve c, which is also a slidevalve, and which, being placedover the port through which the live steam enters the steaml chest,controls the admission ot'steam to either l end of the cylinder. Thecutoff valve e is connected by the rod j' with the cam-yoke g g', whichhas two working-points, each terminating in a friction-roller, t', toreduce the fric i tion of the working-faces of the cams h Ic. The upperor variable cam, It, is the cut-ott' cam, operating to close the cutofic valve e and shut the steam from the steamchest of the cylinder. Thelower cam, k, operates to open the cutoff valve e and admit the steam atthe commencement of each stroke ot' the piston, and, as the steam isadmitted always at the same points, the cam k is keyed fast to the shaftwhich operates the governor, and is not adjustable or capable ofvariation in the relative time of its operation, while the upper orcut-oft' cam, h, is susceptible of variation in its position on thegovernor-shaft relatively to the lower or opening cam, so as to cnt oft'the steam at any point in the stroke of the pistonrod to within a shortdistance of the commencement or end of the stroke.

In Fig. l, l is the governor shaft, which is inserted in the verticalhollow shaft m, with which it is connected by a pin, n, which passesthrough a slot on each side of the hollow shaft m, so that thegovernor-shaft l will revolve with the hollow shaft m, and at the sametime will fall or rise just as the revolutions of the governor o aremore or less rapid. The hollow shaft m is connected with the engine bycrown-wheels p p', or in some other convenient or usual way, so that theincreased or diminished speed of the engine is communicated to thegovernor.

A short hollow cylinder, q, (through which .1 the hollow shaft mpasses,) is attached to the governor-shaft l by the pin n, so that theshort cylinder q revolves with the shat't m and governor-shaft l, whileit also rises and falls with the governor-shaft. This short cylinder qhas two spiral teeth, r i", projecting from the face of the cylinder,the pitch of which is such that each of the teeth passes nearlyhalfround the cylinder in its whole length, as seen in Fig. 4.

These spiral teeth r r fit in corresponding grooves s in the centralcircular hole in the upper or cut-oft' cam, h, through which the spiralcylinder q is inserted.

The cnt-off cam It, the shape of which is shown in Fig. 3, is sositua-ted on the shaft m. as that its acting faces are in the samehorizontal plane as the friction wheel t at the end of the working-pointg of the cam-yoke The cam his not fastened to the spiral cylinder q, norto the shaft fm, but is supported by means of annular attachment t,which rests on a collar, u, on the hollow shaft m, as seen in Figs. land 5. The cam h has no vertical motion on the shaft m or cylinder q,but it is caused to revolve with the governor-shaft l and short cylinderq by means of the spira-l teeth 1' i" iitting in the grooves s. It hasalso another motion on its axis independent ofthe continuous rotarymotion, which will be hereinafter explained.

The lower cam, lr, which opens the cut-off valve e and admits steam, hasits operative faces in a lower plane than those of the cutoit' cam h, asseen in Fig. 1 and the operative point g of the cam-yoke is in the.sameplane as the cam k. The cam k is keyed to the hollow shaft m so as torevolve with it, and has a recess around the shaft m to allow room forthe vertical play of the spiral cylinder q of the cut-oft' cam h.

The operation of our cut off apparatus is as follows: When there is fullhead of steam on and the engine is working too fast, the gov- Ornorrevolves very rapidly, which causes'the governor-shaft l to descend inthe hollow shaft m, and at the same time depresses the spiral cylinderq, which is fastened to the lower end of the governor-rod l, as shown inFig. 5, and lefore described. The depression of the spiral cylinder qcauses the cam 4l1J to turn on its axis on the cylinder q more or less,as the cylinder is more or less depressed, owing to the spiral teeth r ron the cylinder q working in the grooves s in the cam h, for, as thespiral cylinder has a vertical motion with the governorshaft l, and asthe cylinder q, the governorshaft l, and the hollow shaft m are fastenedtogether by the pin n, and as the lower cam, k, is keyed to the hollowshaft m, those parts c lnnot have any relative motion around theircammen axes, although they all revolve together. Now, as the verticalmotion of the short cylinder q inside ofthe cut-off cam h cames that camto move on its axis relatively to the short cylinder q, it will alsoalter the relative position of the upper and lower cams h and 7c and oftheir operative faces. The increase of speed of the governor-shaft l,and the consequent depression of the short cylinder y, will bring theoperative faces h of the cut-oft' cam nearer to the operative faces k ofthe lower cam, as shown in Fig. 2. This position ofthe parts of theapparatus is shown in Figs. 1 and 2, where the camface k of the lowercam has opened the cut-off valve e. As the cam is revolving in thedirection of the arrow in Fig. 2, it will be seen that the camface h ofthe cut-off cam is very close to the operative point t' of the cam-yoke,by which the cut-off valve e will be closed. If, however, the speed ofthe engine should diminish, the governor-rod l would rise and raise withit the spiral cylinder q, which would cause the cut oft' cam h to changeits relative position to the` lower cam, k, and assume the positionshown by dotted lines in Fig. 2, the effectof which would be that thecut-off valve would not be closed until nearer the end of the stroke.

rlhus the relative position of the' operative faces ofthe cams h and kregulates the length of time which elapses betweenthe admission of thesteam and its being cut off, and, as this relative position is alteredby the rise and fall of the goveri'ior-shaft, the cut-ott' valve willpromptly respond in the action to that of the governor.

Having thus described our improved cutoff apparatus, what we. claim asour invention, and desire to secure by Letters Patent, is-

The combination and arrangement of the opening-cam k and cut-oft' cam h,camyoke g g', and the spiral cylinder q, as a cut-off apparatusconstructed substantially as described, with the governor andZcut-offvalve of a steamengine, for the purpose of so regulating the closing ofthe cut-oft' valve as that the point of cut-off shall change with theincreased or diminished force of steam in proportion to the rapidity ot'stroke of the engine, thus forming a variable cut-ofi'.

In testimony whereof, the said GEORGE and ELIHU DoDDs have hereunto settheir hands in presence of us.

GEO. DODDS.

ELIHU DODDS.

Witnesses:

A. S. NrcHoLsoN, J. M. NEAL.

